Liquid crystal display device

ABSTRACT

A black matrix is formed to an edge of a counter substrate. Then, a BM slit, which is an area where the black matrix is not present, is formed in the periphery of a seal material in order to prevent water or moisture from penetrating from the interface between the counter substrate and the black matrix. Then, a light shielding metal is formed in a layer other than a lead line layer, on the side of a TFT substrate, in order to prevent light from leaking from the BM slit. With this structure, it is possible to prevent the light from leaking from the BM slit around a screen. As a result, the degradation of the contrast can be prevented in the periphery of the screen.

CLAIM OF PRIORITY

The present application claims priority from Japanese Patent ApplicationJP 2012-168120 filed on Jul. 30, 2012, the content of which is herebyincorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to a display device, and moteparticularly, to a liquid crystal display device capable of highcontrast with low light leakage around a screen.

BACKGROUND OF THE INVENTION

In a liquid crystal display device, pixels having a pixel electrode anda thin film transistor (TFTs) are arranged in a matrix form in a TFTsubstrate. Further, color filters and the like are formed in a countersubstrate at locations corresponding to the pixel electrodes of the TFTsubstrate. The counter substrate is disposed opposite to the TFTsubstrate with a liquid crystal sandwiched between the TFT substrate andthe counter substrate. Then, an image is formed by controlling theamount of light transmitted through the liquid crystal molecules foreach pixel.

The use of the liquid crystal display device is growing in variousfields due to its flatness and light weight. Compact liquid crystaldisplay devices are widely used in electronic devices such as mobilephones and digital still cameras (DSC). The liquid crystal display paneldoes not emit light by itself, so that it is necessary to have abacklight. If the light from the backlight is not completely blocked inblack display, the contrast of the screen is degraded.

Various methods have been developed to increase the contrast, such asthe use of a light shielding film and a black matrix. However, in thevicinity of the end face of the liquid crystal display panel, it isdifficult to form a light shielding film with high reliability, andthere is a problem of light leakage from the backlight in the peripheryof the screen. In order to prevent the light leakage from the backlightin the periphery of the screen, Japanese Patent Application Laid-OpenNo. 2012-32506 describes a structure in which a light-shielding sealmaterial is formed to the edge of the liquid crystal display panel.

Meanwhile, in order to increase the reliability of the liquid crystaldisplay panel, it is important to ensure the reliability of the sealportion for isolating the inside filled with the liquid crystal from theoutside. There are lead lines extending from the inside to the outsidethrough the seal portion in order to provide scan signals and imagesignals to pixels. At this time, the distance between the TFT substrateand the counter substrate is different in the area where the lead linesexist and in the area where the lead lines do not exist. In order toequalize the distance between the TFT substrate and the countersubstrate, a dummy metal may be provided in the area where the leadlines do not exist.

Japanese Patent Application Laid-Open No. 2005-283862 describes astructure in which, a slit is formed between metals without forming thedummy metal on the entire surface of the area where the lead lines donot exist. With this structure, it is possible to reduce the influenceof the occurrence of static electricity, and to detect defects in theseal material through the slit.

SUMMARY OF THE INVENTION

FIG. 15 is a schematic cross-sectional view of the mechanism of anexisting liquid crystal display device in which the light from thebacklight leaks around the screen, resulting in low contrast in theperiphery of the screen. In FIG. 15, a TFT substrate 100 and a countersubstrate 200 are bonded together by a seal material 20, the inside ofwhich is filled with a liquid crystal 300. A black matrix 202 is formedin the counter substrate 200. If the black matrix 202 is formed to theedge of the counter substrate 200, problems such as the removal of theblack matrix 202 may occur. For this reason, the black matrix is notformed to the edge of the counter substrate 200. Some of the light fromthe backlight repeats total reflection in the TFT substrate 100, whichis emitted from the vicinity of the TFT substrate 100 and the countersubstrate 200 in the direction of the screen.

The liquid crystal display panel is placed in a frame 400 with a flange401. The light incident to the counter substrate 200 at a certain angleis emitted in the direction of the screen, resulting in low contrast. Inorder to prevent this, it is preferable that the black matrix 202 isformed to the edge of the counter substrate 200. However, the liquidcrystal panel is formed in such a way that a large number of liquidcrystal display panels formed in a mother substrate are separated fromeach other by scribing or other suitable method. Thus, a mechanicalstress is applied to the edge of the liquid crystal display panel, sothat if the black matrix 202 is formed to the edge of the countersubstrate 200, there is a problem that the black matrix is likely to beremoved from the edge of the counter substrate 200.

If the black matrix 202 is removed at the edge of the counter substrate200, water enters from the edge where the black matrix 202 is removed,penetrating into the seal portion of the liquid crystal display panelalong the interface between the black matrix 202 and the countersubstrate 200. As a result, the reliability of the liquid crystaldisplay device is degraded. FIG. 16 shows the state in which the waterand the like, entering from the outside penetrates into the seal portionalong the interface between the black matrix 202 and the countersubstrate 200, which is shown by the arrows.

In FIG. 16, a gate insulating film 102, a passivation film 106, and aninter-layer insulating film 108 are formed on the TFT substrate 100.Then, the black matrix 202 and an overcoat film 203 are formed on theside of the counter substrate 200. The TFT substrate 100 and the countersubstrate 200 are bounded to each other by the seal material 20. Theinside of the seal material 20 is filled with the liquid crystal layer300. The arrows in FIG. 16 schematically show the penetration of thewater from the outside into the liquid crystal layer 300 within the sealmaterial 20.

FIG. 17 is a cross-sectional view of the liquid crystal display panel,showing a structure for preventing such a problem. In FIG. 17, the blackmatrix 202 formed in the counter substrate 200 is formed to the edge ofthe counter substrate 200. However, the black matrix 202 is separatedinto outside and inside portions on the outside of the seal material 20by the BM slit 2021. With this structure, the water, and the like,entering from between the black matrix 202 and the counter substrate 200at the edge of the counter substrate 200 is blocked by the BM slit 2021,and will not enter the inside of the BM slit 2021. Thus, the structureshown in FIG. 17 can increase the reliability of the liquid crystaldisplay panel.

FIG. 18 is a plan view of the liquid crystal display device having thestructure described above. In FIG. 18, a display area 10 is formed inthe area where the TFT substrate 100 and the counter substrate 200overlap. The TFT substrate 100 is larger than the counter substrate 200.A terminal portion 30 is formed in the TFT substrate in the area wherethe counter substrate 200 is not present. Then, an IC driver 40 ismounted in the terminal portion 30 to drive the liquid crystal displaydevice. Note that a flexible wiring substrate, not shown, is connectedto the edge of the terminal portion 30 in order to supply power source,scan signals, image signals, and the like.

In FIG. 18, the display area 10 is formed in the area surrounded by theseal material 20. The black matrix 202 is formed inside the countersubstrate 200, extending to the outside of the seal material 20 and tothe edge of the counter substrate 200. On the outside of the sealmaterial 20, the BM slit 2021 is formed in a frame shape around theblack matrix 202, in order to prevent the water, and the like, fromentering from the edge of the black matrix 202.

In this structure, the light may not be blocked in the portion of the BMslit 2021. Thus, the light from the backlight leaks into the screenthrough the BM slit 2021. In order to prevent the light leakage from theBM slit 2021, a metal light shielding film is formed on the side of theTFT substrate at the position corresponding to the BM slit 2021. Themetal may be formed at the time of the formation of the gate electrodelayer, or at the time of the formation of the drain electrode layer.

As described above, the BM slit 2021 is shielded from the light on theside of the TFT substrate 100. FIG. 19 is a cross-sectional view of thisstate. In the example of FIG. 19, a light shielding metal 14 is a metalformed at the time of the formation of the drain layer. The light fromthe backlight is blocked by the light shielding metal 14, so that thelight does not leak from the BM slit 2021 to the outside. The otherconfigurations shown in FIG. 19 are the same as those described in FIG.16 or FIG. 17. As shown in FIGS. 18 and 19, the width of the lightshielding metal 14 is greater than the width of the BM slit 2021.

As shown in FIG. 18, it is possible to shield the liquid crystal displaypanel from the light from the backlight by the light shielding metal 14in the three sides where lead lines 11 are not formed. However, it isdifficult to form the light shielding metal 14 in the side where thelead lines 11 are present in the same way as in the other three sides ofthe liquid crystal display panel. In other words, the light shieldingmetal 14 is formed at the time of the formation of the gate layer or thedrain layer, so that the lead lines 11 may be short-circuited by thelight shielding metal 14 in the area where the lead lines 11 arepresent. Here, the lead lines 11 are the lines for connecting scanlines, image signal lines (drain lines), common lines, and the like inthe display area 10, to the IC driver 40 provided in the terminalportion 30.

FIGS. 20A, 20B, and 20C are enlarged views of the F portion of FIG. 18where the lead lines 11 are present. FIG. 20A is an enlarge plan view ofthe portion of the lead lines in the TFT substrate 100. FIG. 20B is anenlarged plan view of the state of the black matrix 202 and the BM slit2021 in the counter substrate 200. FIG. 20C is a plan view in thevicinity of the BM slit 2021 when the TFT substrate 100 and the countersubstrate 200 overlap. In FIG. 20C, although the MB slit 2021 isshielded from the light in the area where the lead lines 11 are present,the light from the backlight passes through the portion T where the leadlines 11 are not present. As a result, the contrast is reduced in theperiphery of the screen.

The purpose of the present invention is to block the light coming fromthe backlight also in the area where the lead lines 11 are present inFIG. 18, and to prevent degradation of the contrast in the periphery ofthe screen.

The present invention is to overcome the above problem, and specificaspects are as follows.

(1) In a liquid crystal display device, pixels having a TFT and a pixelelectrode are arranged in a matrix form in a TFT substrate. Further,color filters and the like are formed in a counter substrate atlocations corresponding to the pixel electrodes of the TFT substrate.The TFT substrate and the counter substrate are bonded together by aseal material. Then, a liquid crystal is sandwiched between the TFTsubstrate and the counter substrate. The black matrix is formed to anedge of the counter substrate. A BM slit, which is an area where theblack matrix is not present, is formed in the entire periphery of theblack matrix on the outside of the seal material with a predeterminedwidth wb. A light shielding metal is formed in the entire periphery ofthe TFT substrate in the area facing the BM slit, with a predeterminedwidth wm. The width wm is greater than the width wb.

(2) In a liquid crystal display device, pixels having a TFT and a pixelelectrode are arranged in a matrix form in a TFT substrate. Further,color filters and the like are formed in a counter substrate atlocations corresponding to the pixel electrodes of the TFT substrate.The TFT substrate and the counter substrate are bonded together by aseal material. Then, a liquid crystal is sandwiched between the TFTsubstrate and the counter substrate. A display area is formed in thearea where the TFT substrate and the counter substrate overlap. The TFTsubstrate is larger than the counter substrate. A terminal portion isformed in the TFT substrate in the area where the counter substrate isnot present. Lead lines are formed in the terminal portion to connect tothe lines in the display area. The black matrix is formed to an edge ofthe counter substrate. A BM slit, which is an area where the blackmatrix is not present, is formed in the entire periphery of the blackmatrix on the outside of the seal material with a predetermined widthwb. Further, a light shielding metal is formed in the entire peripheryof the TFT substrate at the position corresponding to the BM slit and ina layer other than the layer of the lead lines, with a predeterminedwidth wm. The width wm is greater than the width wb.

According to the present invention, the black matrix can be formed tothe peripheral portion, so that it is possible to prevent the leakage ofthe light from the backlight around the screen and increase the contrastin the periphery of the screen. Further, according to the presentinvention, the BM slit is formed on the outside of the seal material inorder to increase the reliability of the sealing. Then, the lightshielding metal is formed in the TFT substrate in order to shield the BMslit from the light around the entire periphery. As a result, it ispossible to increase the contrast of the entire screen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional structure of IPS-PRO of a common toptype;

FIG. 2 shows a cross-sectional structure of IPS-LITE;

FIG. 3 is a plan view of a first embodiment;

FIGS. 4A, 4B, and 4C are enlarged views of the A portion in the firstembodiment;

FIG. 5 is a plan view of a second embodiment;

FIGS. 6A, 6B, and 6C are enlarged views of the B portion in the secondembodiment;

FIG. 7 is a plan view of a third embodiment;

FIGS. 8A, 8B, and 8C are enlarged views of the C portion in the thirdembodiment;

FIG. 9 is a plan view of a fourth embodiment;

FIGS. 10A, 10B, and 10C are enlarged views of the D portion in thefourth embodiment;

FIG. 11 is a plan view of a fifth embodiment;

FIGS. 12A, 12B, and 12C are enlarged views of the E portion in the fifthembodiment;

FIG. 13 is a cross-sectional view of the seal portion in a sixthembodiment;

FIG. 14 is a plan view of the sixth embodiment;

FIG. 15 is a schematic cross-sectional view of the problem in theconventional example;

FIG. 16 is a schematic cross-sectional view of the problem in anotherconventional example;

FIG. 17 is a cross-sectional view of the structure for solving theproblem shown in FIG. 16;

FIG. 18 is a plan view of the conventional example;

FIG. 19 is a cross-sectional view of the structure for solving part ofthe problem of the conventional example; and

FIGS. 20A, 20B, and 20C are enlarged views of the problem of theconventional example shown in FIG. 18.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

There are various types of the liquid crystal display device such as IPS(In Plane Switching) type, TN type, and VA type. The present inventioncan be applied to all of these types. The present invention uses a metallight shielding film in the TFT substrate. The metal light shieldingfilm is formed at the same time when electrodes and lines are formed bymetal in the TFT substrate. Thus, the cross-sectional structure of aliquid crystal display panel is described first for the laterdescription. There are many different types in the liquid crystaldisplay device, and it is difficult to describe all of them. Thus, thecross-sectional structures of the so-called IPS-PRO type and IPS-LITEtype will be described as typical examples.

FIG. 1 is a cross-sectional view of a liquid crystal display device of atype that is called IPS-PRO, or the so-called common top type. In FIG.1, a gate electrode 101 is formed on a TFT substrate 100 of glass, and agate insulating film 102 is formed on the TFT substrate 100 so as tocover the gate electrode 101. The gate electrode 101 is Al alloy, MoWalloy, or MoCr alloy, or a film formed by laminating these metals. Asemiconductor layer 103 is formed above the gate electrode 101 with thegate insulating film 102 between them. A drain electrode 104 and asource electrode 105 are formed on the semiconductor layer 103. Thedrain electrode 104 and the source electrode 105 face each other with achannel area between them. The drain electrode 104 is connected to animage signal line (drain line) 133 at a position not shown. The drainelectrode 104 and the source electrode 105 are Al alloy, MoW alloy, orMoCr alloy, or a film formed by laminating these metals.

An inorganic passivation film 106 of SiN, and the like, is formed on thesemiconductor layer 103. The inorganic passivation film 106 covers theelectrode 104 and the source electrode 105. Then, a pixel electrode 107is formed by an ITO on the entire surface of the inorganic passivationfilm 106. The pixel electrode 107 and the source electrode 105 extendingfrom the TFT are connected to each other through a through hole formedin the inorganic passivation film 107. An inter-layer insulating film108 is formed on the pixel electrode 107. Then a common electrode 109with a slit 1091 is formed on the inter-layer insulating film 108.

The common electrode 109 is commonly formed all over the screen. Thecommon electrode 109 is formed by ITO (Indium Tin Oxide), which is atransparent electrode. The ITO has a large electrical resistance. Thus,a common metal 110 with a low resistance is formed on the commonelectrode 109 in the area where the light does not penetrate, in orderto equalize the potential of the whole common electrode 109. In thepresent invention, the common metal 110 may also be used as the lightshielding metal. The common metal 110 is Al alloy, MoW alloy, or MoCralloy, or a film formed by laminating these metals. An orientation film111 is formed so as to cover the common electrode 109 and the commonmetal 110.

In FIG. 1, the counter substrate 200 is disposed opposite the TFTsubstrate with the liquid crystal layer 300 between them. The blackmatrix 202 and the color filter 201 are formed on the counter substrate200, on which the overcoat film 203 is formed so as to cover the blackmatrix 202 and the color filter 201. Then, the orientation film 111 isformed on the overcoat film 203. In the TFT substrate 100 shown in FIG.1, when a voltage is applied to the pixel electrode 107, electric fieldlines are generated between the common electrode 109 and the pixelelectrode 110, rotating the liquid crystal molecules to control thetransmittance of the liquid crystal 300 for each pixel. Thus, an imageis formed.

FIG. 2 is a cross-sectional view of the liquid crystal display device ofIPS type, which is the so-called IPS-LITE. The IPS-LITE is the commontop type in which the common electrode 109 is formed on the top layer.In FIG. 2, the gate electrode 101, the gate insulating film 102, thesemiconductor layer 103, the drain electrode 104, and the sourceelectrode 105 are formed on the TFT substrate 100, by the same processas in the IPS-PRO type described above. In FIG. 2, after the drainelectrode 104 and the source electrodes 105 are formed, the pixelelectrode 107 is formed by ITO without the insulating film therethrough.

The inorganic passivation film 106 is formed by SiN, and the like, onthe pixel electrode 107. Then, the common electrode 109 is formed on theinorganic passivation film 106. The common electrode has the slit 1091at the position corresponding to the pixel. The common electrode 109 iscommonly formed on the entire screen. The common metal 110 is formed onthe common electrode 109 in the area where the light does not penetrate,in order to equalize the potential of the common electrode 109. In thepresent invention, the common metal 110 may also be used as the lightshielding metal.

In FIG. 2, the counter substrate 200 is disposed opposite the TFTsubstrate with the liquid crystal layer 300 between them. The structureof the counter substrate 200 is the same as the case of the IPS-PROdescribed in FIG. 1, so that the description thereof will be omitted.The present invention will be described in detail with reference to thepreferred embodiments.

First Embodiment

FIG. 3 is a plan view of a liquid crystal display device, showing thestructure of a first embodiment. The structure of FIG. 3 is the same asthe structure of FIG. 18, except the part where lead lines 12 exist. Inother words, in FIG. 3, the black matrix 202 is formed to the endsurface of the counter substrate 200. Then, a BM slit 2021 is formed inthe entire periphery of the black matrix 202 on the outside of the sealmaterial in order to prevent the water and the like from penetrating theliquid crystal display panel from the interface between the black matrix202 and the counter substrate 200.

FIG. 3 is different from FIG. 18 in that the light shielding metal 142is also formed on the side where the lead lines 12 are formed, on theside of the TFT substrate. FIGS. 4A, 4B, and 4C are enlarged views ofthe A portion of FIG. 3. FIG. 4A is a plan view of the lead lines 12 andthe light shielding metal 142 on the side of the TFT substrate 100. FIG.4B shows the black matrix 202 and the BM slit 2021 on the inside of thecounter substrate 200. FIG. 4C is a plane view showing the state inwhich the TFT substrate 100 and the counter substrate 200 overlap.

In FIG. 4A, the lead lines 12 are the gate lead lines 12 formed in thesame layer as the gate electrode. The drain light shielding metal 142 isformed so as to cover the gate lead lines 12 on the same layer as thedrain electrode at the position corresponding to the BM slit 2021 shownin FIG. 4B. In FIG. 4A, the gate lead lines 12 and the drain lightshielding metal 142 are formed in the different layers with the gateinsulating film between them. Thus, a short circuit does not occurbetween the gate lead lines 12 and the drain light shielding film 142.

FIG. 4C is a plane view showing the state in which the TFT substrate 100and the counter substrate 200 overlap in the vicinity of the BM slit2021. As shown in FIG. 4C, the BM slit 2021 is covered by the drainlight shielding metal 142 from the bottom on the side of the TFTsubstrate 100. Thus, the light from the backlight does not pass throughthe BM slit 2021. The width wm of the drain light shielding metal 142 isgreater than the width wb of the BM slit 2021. For example, the width wbof the BM slit 2021 is 30 to 50 μm, and the width wm of the drain lightshielding metal 142 is 50 to 80 μm. The example of the widths is thesame as in the other embodiments.

As described above, in the present embodiment, the lead lines 12 areformed in the same layer as the gate electrode, and the light shieldingmetal 142 is formed in the same layer as the drain electrode. Thus, theBM slit 2021 formed in the counter substrate 200 can be completelyshielded from the light, also in the area where the lead lines 12 areformed. As a result, it is possible to achieve better contrast allaround the screen.

Second Embodiment

FIG. 5 is a plan view of a liquid crystal display device, showing thestructure of a second embodiment. The structure of FIG. 5 is the same asthe structure of FIG. 3, except the area where lead lines 13 arepresent. In other words, in FIG. 5, the black matrix 202 is formed tothe edge of the counter surface 200, and the BM slit 2021 is formed inthe entire periphery of the black matrix on the outside of the sealmaterial 20, in order to prevent water or moisture from penetrating theliquid crystal display panel from the interface between the black matrix202 and the counter substrate 200.

Also in FIG. 5, in a similar way to FIG. 3, the light shielding metal141 is formed on the side where the lead lines 13 are formed, on theside of the TFT substrate 100. FIG. 5 is different from FIG. 3, which isthe first embodiment, in that the relationship between the lead lines 13and the light shielding metal 141 is reversed. FIGS. 6A, 6B, and 6C areenlarged views of the B portion of FIG. 5. FIG. 6A is a plan view of thelead lines 13 and the light shielding metal 141 on the side of the TFTsubstrate 100. FIG. 6B shows the black matrix 202 and the BM slit 2021on the inside of the counter substrate 200. FIG. 6C is a plan viewshowing the state in which the TFT substrate 100 and the countersubstrate 200 overlap.

In FIG. 6A, the lead lines 13 are the drain lead lines 13 formed in thesame layer as the drain electrode. The gate light shielding metal 141 isformed in the same layer as the gate electrode at the positioncorresponding to the BM slit 2021 shown in FIG. 6B. The gate lightshielding metal 141 covers below the drain lead lines 13. In FIG. 6A,the drain lead lines 13 and the gate light shielding metal 141 areformed in the different layers with the gate insulating film betweenthem. Thus, a short circuit does not occur between the drain lead lines13 and the gate light shielding metal 141.

FIG. 6C is a plan view showing the state in which the TFT substrate 100and the counter substrate 200 overlap in the vicinity of the BM slit2021. As shown in FIG. 6C, the BM slit 2021 is covered by the gate lightshielding metal 141 from the bottom on the side of the TFT substrate100. Thus, the light from the backlight does not pass through the BMslit 2021. The width wm of the gate light shielding film 141 is greaterthan the wide wb of the BM slit 2021. For example, the width wb of theBM slit 2021 is 30 to 50 μm and the width wm of the gate light shieldingmetal 141 is 50 to 80 μm.

As described above, in the present embodiment, the lead lines 13 areformed in the same layer as the drain electrode, and the light shieldingmetal 141 is formed in the same layer as the gate electrode layer. Thus,the BM slit 2021 formed in the counter substrate 200 can be completelyshielded from the light, also in the area where the lead lines 13 areformed. As a result, it is possible to achieve better contrast allaround the screen.

Third Embodiment

FIG. 7 is a plan view of a liquid crystal display device, showing thestructure of a third embodiment. The structure of FIG. 7 is the same asthe structure of FIG. 3, except the area where lead lines 11 arepresent. In other words, in FIG. 7, the black matrix 202 is formed tothe edge of the counter substrate 200, and the BM slit 2021 is formed inthe entire periphery of the black matrix on the outside of the sealmaterial 20, in order to prevent water or moisture from penetrating theliquid crystal display panel from the interface between the black matrix202 and the counter substrate 200.

Also in FIG. 7, in a similar way to FIG. 3, a light shielding metal 143is formed on the side where the lead lines 11 are formed, on the TFTsubstrate. FIG. 7 is different from FIG. 3 of the first embodiment orfrom FIG. 5, which is the second embodiment, in that the light shieldingmetal 143 is formed by the common light shielding metal 143. FIGS. 8A,8B, and 8C are enlarged views of the C portion of FIG. 7. FIG. 8A is aplan view of the lead line 11 and the light shielding metal 143 on theside of the TFT substrate 100. FIG. 8B shows the black matrix 202 andthe BM slit 2021 on the inside of the counter substrate 200. FIG. 8C isa plan view showing the state in which the TFT substrate 100 and thecounter substrate 200 overlap.

In FIG. 8A, the lead line 11 includes the drain lead line 13 formed inthe same layer as the drain electrode, and the gate lead line 12 formedin the same layer as the gate electrode. The common light shieldingmetal 143 is formed in the same layer as the common metal at theposition corresponding to the BM slit 2021 shown in FIG. 8B. The commonlight shielding metal 143 covers the gate lead line 12 and the drainlead line 13. In FIG. 8A, the gate lead line 12 or the drain lead line13, and the common light shielding metal 143 are formed in the differentlayers with the inorganic passivation film and the like between them.Thus, a short circuit does not occur between the gate lead line 12 orthe drain lead line 13, and the common light shielding metal 143.

FIG. 8C is a plan view showing the state in which the TFT substrate andthe counter substrate 200 overlap in the vicinity of the BM slit 2021.As shown in FIG. 8C, the BM slit 2021 is covered by the common lightshielding metal 143 from the bottom on the side of the TFT substrate100. Thus, the light from the backlight does not pass through the BMslit 2021. In the present embodiment, the conditions are the same asthose in the first or second embodiment, such as that the width wm ofthe common light shielding metal 143 is greater than the width wb of theBM slit 2021.

As described above, in the present embodiment, the lead lines 11 can beformed in multiple layers, such as in the same layer as the gateelectrode or in the same layer as the drain electrode. Thus, the presentembodiment can be applied to the case in which the density of the leadlines 11 is greater than the case in the first or second embodiment.Further, it is possible to completely shield the BM slit 2021 from thelight from the backlight by the common light shielding metal 143. As aresult, better contrast can be achieved all around the screen.

Fourth Embodiment

FIG. 9 is a plan view of a liquid crystal display device, showing thestructure of a fourth embodiment. The structure of FIG. 9 is the same asthe structure of FIG. 3, except the area where the lead lines 11 arepresent. In other words, in FIG. 9, the black matrix 20 is formed to theedge of the counter substrate 200, and the BM slit 2021 is formed in theentire periphery of the black matrix on the outside of the seal material20, in order to prevent water or moisture from penetrating the liquidcrystal display panel from the interface between the black matrix 202and the counter substrate 200. Also in FIG. 9, in a similar way to thefirst to third embodiments, the light shielding metal 14 is formed onthe side where the lead line 11 is formed, on the side of the TFTsubstrate 100.

In FIG. 9, which is the present embodiment, the planar shape of the leadlines 11 is different from that of the first to third embodiments. Inother words, the lead lines 11 shown in FIG. 9 are not only diagonallines. They include a portion of diagonal lines as well as a portionthat is parallel to the liquid crystal display panel. FIGS. 10A, 10B,and 10C are enlarged views of the D portion of FIG. 9. In FIG. 10A, theline pitch in the diagonal line portion Q is smaller than in the lineportion P that is parallel to the side of the liquid crystal displaypanel. In this portion, it is preferable that the lead lines 11 areprovided separately with the gate lead line 12 and drain lead line 13,in order to ensure isolation between the lines. Meanwhile, in theportion P that is parallel to the side of the liquid crystal displaypanel, it is possible to set the line pitch larger than the line pitchin the diagonal line portion Q.

In FIG. 10A, the drain lead line 13, which is the diagonal line Q,switches to the gate lead line 12 through the through hole 50 in thecurved portion from the diagonal portion Q to the portion P that isparallel to the side of the liquid crystal display panel. Thus, in theportion P that is parallel to the side of the liquid crystal displaypanel, the lead line 11 can be formed only by the gate lead line 12 inthe same layer as the gate electrode. In such a case, the drain lightshielding metal 142 formed in the same layer as the drain electrode canbe used as the light shielding metal.

FIG. 10C is a plan view showing the state in which the TFT substrate 100and the counter substrate 200 overlap in the vicinity of the BM slit2021. As shown in FIG. 10C, the BM slit 2021 is covered by the drainlight shielding metal 142 from the bottom on the side of the TFTsubstrate 100. Thus, the light from the backlight does not pass throughthe BM slit 2021.

As described above, in the present embodiment, the gate lead lines 12and the drain lead lines 13 are used as the lead lines 11 in thediagonal line portion with a small pitch. Then, only the gate lead lines12 are used as the lead lines 11 in the large-pitch portion that isparallel to the side of the liquid crystal display panel (hereinafterreferred to as the parallel line). Thus, the drain shielding metal canbe used as the light shielding metal for the BM slit 2021, so that thereis no need to form another new metal as the light shielding metal.

In the above description, it is assumed that the diagonal lines are thetwo-layer lines and the parallel lines are the gate lead lines 12.However, this structure can be reversed such that the diagonal lines arethe two-layer lines and the parallel lines are the drain lines 13. Insuch a case, the gate light shielding metal 141 is used as the lightshielding metal.

Fifth Embodiment

FIG. 11 is a plan view of a liquid crystal display device, showing thestructure of a fifth embodiment. The structure of FIG. 11 is the sane asthe structure of FIG. 3, except the area where the lead line 11 arepresent. In other words, in FIG. 11, the black matrix 202 is formed tothe edge of the counter substrate 200, and the BM slit 2021 is formed inthe entire periphery of the black matrix on the outside of the sealmaterial 20, in order to prevent water or moisture from penetrating theliquid crystal display panel from the interface between the black matrix202 and the counter substrate 200. Also in FIG. 11, in a similar way tothe first to fourth embodiments, the light shielding metal 142 is formedon the side where the lead lines 11 are formed, on the side of the TFTsubstrate 100.

In FIG. 11, which is the present embodiment, the planar shape of thelead lines 11 is different from that of the first to third embodiments.In other words, the lead lines shown in FIG. 11 are the diagonal lines,and switch from the diagonal lines to the parallel lines and back to thediagonal lines again. FIGS. 12A, 12B, and 12C are enlarged views of theE portion of FIG. 11. In FIG. 12A, the lead lines in the diagonal lineportion are two-layer lines of the gate lead line 12 and the drain leadline 13. Then, the lead lines in the parallel line portion are two-layerlines of the gate lead line 12 and a bridging ITO 15. In this case, thedrain light shielding metal 142 formed in the same layer as the drainelectrode is used as the light shielding metal.

In FIG. 12A, the gate lead line is formed below the drain lightshielding metal, and the bridging ITO is formed above the drain lightshielding metal. The lead lines switch back to the diagonal lines afterthe position corresponding to the light shielding metal, which aretwo-layer lines of the gate lead line 12 and the drain lead line 13. Atthis time, the bridging ITO 15 switches to the drain lead line 13through the through hole 50.

The drain light shielding metal 142 is formed in the TFT substrate 100at the position corresponding to the BM slit 2021 formed in the countersubstrate 200 shown in FIG. 12B. FIG. 12C is a plan view showing thestate in which the TFT substrate 100 and the counter substrate 200overlap in the vicinity of the BM slit 2021. In FIG. 12C, the BM slit2021 is completely covered by the drain light shielding metal 142 fromthe bottom. The gate lead line 12 and the bridging ITO 15 are present inthe area of the BM slit 2021.

For example, in IPS-PRO, when the bridging ITO 15 is formed by using thepixel electrode 107, the formation of the through hole in thepassivation film 106 and the connection to the drain lead line 13 can beperformed at the same time as the process in the pixel portion, in whichthe through hole is formed in the passivation film 106 and the pixelelectrode 107 is connected to the source electrode 105. Thus, it ispossible to form the bridging ITO 15 without increasing the number ofsteps.

In the structure described above, when the diagonal line switches to theparallel line, the drain lead line 13 switches to the bridging ITO 15.However, it is also possible that the gate lead line 12 switches to thebridging ITO 15. In such a case, the gate light shielding metal 141 isused as the light shielding metal.

Note that, as shown in FIG. 11, when the lead lines switch from thediagonal lines to the parallel lines and back to the diagonal lines, itis also possible to use other line structures than the line structureshown in FIGS. 12A, 12B, and 12C. The first structure is as follows: Thediagonal lines are two-layer lines of the drain lead line 13 and thegate lead line 12. Then, the drain lead line 13 switches to the gatelead line 12 in the parallel line portion through the through hole 50.Thus, the lead lines in the parallel line portion are only the leadlines 12. In this case, the drain light shielding metal 142 is used asthe light shielding metal. When the parallel lines switch to thediagonal lines, the lead lines are back again to the two-layer lines ofthe drain lead line 13 and the gate line 12 through the through hole 50.

The second structure is as follows: The diagonal lines are two-layerwiring of the drain lead line 13 and the gate lead line 12 similarly asshown in FIG. 12. Then, the gate lead line 12 switches to the drain leadline 13 through the through hole 50 in the parallel line portion. Thus,the lead lines are only the drain lead lines 13 in the parallel lineportion. In this case, the gate light shielding metal 141 is used as thelight shielding metal. When the parallel line switches to the diagonalline, the lead lines are back again to the two-layer lines of the drainlead line 13 and the gate lead line 12 through the through hole 50.

Sixth Embodiment

As shown in FIG. 11 or 12, when the bridging ITO 15 is used as the leadline 11, the following problem may occur if the ITO of the commonelectrode 109 in IPS-LITE is used as the ITO. The common electrode 109in IPS-LITE is formed on the top layer above the passivation film 106.In other words, the insulating film is not present on the ITO. Theadhesive strength between the ITO and the seal material 20 is smallerthan the adhesive strength between the insulating film and the sealmaterial. For this reason, the reliability of the seal material 20 maybe degraded.

Meanwhile, the light shielding metal 14 should be formed at the positioncorresponding to the bridging ITO 15. In this case, as shown in FIG. 13,the BM slit 2021 in the counter substrate 200 is formed to overlap theseal material 20, and the bridging ITO 15 is also formed to overlap theseal material 20. In this way, the contact between the bridging ITO 15and the seal material 20 can be achieved in such a way that the bridgingITO 15 overlaps only a portion of the width of the seal material 20,instead of the entire width of the seal material 20. In this way, it ispossible to prevent the reduction in the adhesive reliability of theseal portion.

FIG. 14 is an example in which the BM slit 2021 and the bridging ITO areformed within the width of the seal material 20 as shown in FIG. 13. InFIG. 14, on the side where the lead lines not shown are formed, the stepportion V is provided in the BM slit 2021 and the light shielding metal14 so that the seal material 20, the BM slit 2021, and the bridging ITOcan be formed in a portion of the seal material 20 within the widththereof. The same effect can also be obtained by providing the step inthe seal material in the reverse direction, instead of providing thestep portion in the BM slit 2021 and the light shielding metal 14.

What is claimed is:
 1. A liquid crystal display device, wherein a TFTsubstrate in which pixels having a TFT and a pixel electrode arearranged in a matrix form, and a counter substrate in which a colorfilter and a black matrix are formed are bonded together by a sealmaterial, with liquid crystal sandwiched between the TFT substrate andthe counter substrate, wherein the black matrix is to formed to an edgeof the counter substrate, wherein a BM slit, which is an area where theblack matric is not present, is formed in the entire periphery of theblack matrix on the outside of the seal material, with a predeterminedwidth wb, wherein a light shielding metal is formed in the entireperiphery of the TFT substrate at the position corresponding to the BMslit, with a predetermined width wm, and wherein, the width wm isgreater than the width wb.
 2. The liquid crystal display deviceaccording to claim 1, wherein the light shielding metal is formed in thesame layer as a drain electrode formed in the TFT substrate.
 3. Theliquid crystal display device according to claim 1, wherein the lightshielding metal is formed in the same layer as a gate electrode formedin the TFT substrate.
 4. The liquid crystal display device according toclaim 1, wherein the light shielding metal is formed in the same layeras a common metal connected to a common electrode formed in the TFTsubstrate.
 5. A liquid crystal display device, wherein a TFT substratein which pixels having a TFT and a pixel electrode are arranged in amatrix form, and a counter substrate in which a color filter and a blackmatrix are formed are bonded together by a seal material, with liquidcrystal sandwiched between the TFT substrate and the counter substrate,wherein a display area is formed in an area where the TFT substrate andthe counter substrate overlap, wherein the TFT substrate is larger thanthe counter substrate, wherein a terminal portion is formed in the TFTsubstrate in the area where the counter substrate is not present,wherein lead lines are formed in the terminal portion to connect to thelines in the display area, wherein the black matrix is formed to an edgeof the counter substrate, wherein a BM slit, which is an area where theblack matrix is not present, is formed in the entire periphery of theblack matrix on the outside of the seal material, with a predeterminedwidth wb, wherein a light shielding metal is formed in the entireperiphery of the TFT substrate at the position corresponding to the BMslit and in a layer other than the layer of the lead lines, with apredetermined width wm, and wherein the width wm is greater than thewidth wb.
 6. The liquid crystal display device according to claim 5,wherein the light shielding metal is formed in the same layer as a drainelectrode formed in the TFT substrate.
 7. The liquid crystal displaydevice according to claim 5, wherein the light shielding metal is formedin the same layer as a gate electrode formed in the TFT substrate. 8.The liquid crystal display device according to claim 5, wherein thelight shielding metal is formed in the same layer as a common metalconnected to a common electrode formed in the TFT substrate.